High availability and multipathing for fibre channel over ethernet

ABSTRACT

A physical Fiber Channel over Ethernet (FCoE) switch defines a multipath virtual FCoE switch to provide uninterrupted storage access between N_PORTs of an FCoE host and a Fiber Channel (FC) storage target, for example, in response to an F_PORT failure. Through the multipath virtual FCoE switch, the fabric is configured with multiple physical paths available between the FCoE hosts and FC targets. The multipath virtual FCoE switch is defined between or among multiple physical FCoE switches coupled to the Ethernet fabric. One of the F_PORTs is designated as being in the primary FCoE path, while any other F_PORTs sharing the virtual FCoE switch are reserved for standby paths in case the primary FCoE path is disabled. When a failure to a primary FCoE path is detected, a standby path is promoted to become a new primary FCoE path and subsequent traffic is routed in both directions through the new primary FCoE path.

BACKGROUND

A storage area network (SAN) may be implemented as a high-speed, specialpurpose network that interconnects different kinds of data storagedevices with associated data servers on behalf of a large network ofusers. Typically, a storage area network includes high performanceswitches as part of the overall network of computing resources for anenterprise. The storage area network is usually clustered in closegeographical proximity to other computing resources, such as mainframecomputers, but may also extend to remote locations for backup andarchival storage using wide area network carrier technologies. FibreChannel networking is typically used in SANs although othercommunications technologies may also be employed, including Ethernet andIP-based storage networking standards (e.g., iSCSI, FCIP (Fibre Channelover IP), etc.).

As used herein, the term “Fibre Channel” refers to the Fibre Channel(FC) family of standards (developed by the American National StandardsInstitute (ANSI)) and other related and draft standards. In general,Fibre Channel defines a transmission medium based on a high speedcommunications interface for the transfer of large amounts of data viaconnections between varieties of hardware devices.

In a typical SAN, one or more FC switches are used to communicativelyconnect one or more server devices with one or more data storagedevices. Such switches generally support a high performance switchingfabric and provide a number of communication ports for connecting toother switches, servers, storage devices, or other SAN devices. Otherhigh performance fabrics may employ different fabric technologies, suchas Infiniband.

Other networking technologies, such as Ethernet, may also be employed incommunicating between computing and networking devices. An evolvingstandard referred to as Fibre Channel over Ethernet (FCoE), for example,is modeled as a Layer3 protocol on top of a Convergence EnhancedEthernet (CEE) fabric. A typical topology includes FCoE switchesconnected at a boundary between a Fibre Channel fabric and a CEE fabric.When deployed in such a multi-protocol fabric, an FCoE F_PORT is theprimary interface for all storage traffic between an FCoE N_PORT (e.g.,of an FCoE host) and an FC resident storage target. As such, failure (ordisabling) of the FCoE F_PORT can significantly disrupt I/O between FCoEhosts in the CEE fabric and FC targets that are interconnected in the FCfabric. For example, in a typical configuration, an N_PORT of an FCoEhost is required to initiate Link Keep Alive Extended Link Services (LKAELS) between the FCoE N_PORT and the FCoE F_PORTs in the Fibre Channelfabric. When an FCoE F_PORT failure is detected, the FCoE N_PORT isrequired to initiate a new FLOGI, followed by a PLOGI to each FC target,to revive communications. Such disruptions in communications areundesirable, and the existing approach is not well scalable.

SUMMARY

Implementations described and claimed herein address the foregoingproblems by using a multipath virtual FCoE switch to provideuninterrupted storage access between FCoE N_PORTs of an FCoE host and anFC storage target, for example, in the presence of an FCoE F_PORTfailure. Through the multipath virtual FCoE switch, an FCoE fabric isconfigured with multiple physical paths available between the FCoE hostsand FC targets. Accordingly, a transparent path switchover among suchpaths may be effected when an active FCoE F_PORT fails, therebypreserving uninterrupted communications between the FCoE hosts and theFC storage targets.

In support of the described technology, a multipath virtual FCoE switchis defined between or among multiple physical FCoE switches coupled tothe Ethernet fabric. On the multipath virtual FCoE switch, a virtualFCoE F_PORT is defined for each physical FCoE F_PORT coupled to theEthernet fabric. The physical FCoE switches create the multipath virtualFCoE switch, which is assigned its own domain ID. The multipath virtualFCoE switch then forms a logical Inter Switch Link (ISL) with each FCoEswitch interfacing with the CEE fabric. The ISLs create logical FSPFadjacencies between the multipath virtual FCoE switch and the physicalFCoE switches, thereby advertising the reachability of the multipathvirtual FCoE switch through at least two physical FCoE switches in theFCoE fabric.

More than two physical FCoE switches may be employed in thismultipathing configuration. One of the FCoE F_PORTs on one of thephysical FCoE switches is designated as being in the primary FCoE path,while any other F_PORTs sharing the multipath virtual FCoE switch arereserved for standby paths in case the primary FCoE path is disabled.When a failure to a primary FCoE path is detected (e.g., the primaryphysical FCoE switch, the primary physical FCoE F_PORT, or the physicallink with the CEE fabric is disabled), one of the auxiliary paths ispromoted to become a new primary FCoE path and subsequent traffic isrouted in both directions through the new primary FCoE path, effectivelymaintaining uninterrupted communications in both directions between theFCoE hosts and the FC storage targets.

Other implementations are also described and recited herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary computing and storage frameworkincluding a local area network (LAN) and a storage area network (SAN).

FIG. 2 illustrates an example high availability configuration includinga multipath virtual FCoE switch defined between two physical FCoEswitches.

FIG. 3 illustrates an example high availability configuration includinga multipath virtual FCoE switch defined between two physical FCoEswitches and showing ownership of a MAC address of a virtual FCoEF_PORT.

FIG. 4 illustrates an example high availability configuration withcommunications through a primary physical FCoE path.

FIG. 5 illustrates example operations for setting up a high availabilityconfiguration with communications through a primary physical FCoE path.

FIG. 6 illustrates an example high availability configuration includinga multipath virtual FCoE switch defined by two physical FCoE switches,after a path switchover.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary computing and storage frameworkincluding a local area network (LAN) 100 and a storage area network(SAN) 102. A local area network (LAN) 100 provides communicationconnectivity among multiple devices, such as a workstation 116 and hosts114. Connectivity within the LAN 100 is provided by switches 106, 107and 108. The LAN 100 is presumed to be the network for a relevantenterprise with a number of different segments, although any LANconfiguration may be employed.

A storage area network (SAN) 102 resides within the LAN 100 and providescommunication connectivity, routing, and other SAN functionality amonghosts 110 and storage units 112. The SAN 102 includes a number ofswitches, such as switches 101, 103 and 104. Switches 101, 103 and 104,for example, may be configured as a set of blade components insertedinto a chassis, as rackable or stackable modules, or as other devicestructures. In one implementation, the chassis has a back plane ormid-plane into which the various blade components, such as switchingblades and control processor blades, may be inserted.

Two of the switches, i.e., switches 103 and 104, of the SAN 102 areconnected within the LAN 102 via a switch 106. The switch 106 is alsoused to join other segments of the LAN 100, as represented by the otherswitches 107 and 108, which are also shown in the LAN 100. In addition,a series of hosts 110 are connected to various switches 104 in the SAN102. Likewise, storage units, such as described storage units 112, areconnected also to various switches 104 in the SAN 102.

Various application clients, such as the workstation 116, are networkedto application servers, such as the hosts 114, via the LAN 100. A usercan access applications resident on the hosts 114 through theworkstation 116. The applications may depend on data (e.g., an emaildatabase) stored at one or more of the storage units 112. Accordingly,in the illustrated example, the SAN 102 provides connectivity among thehosts 114, the workstation 116, and the application data storage devices112 to allow the applications to access the data they need to operate.

The hosts 114 and switches 103 and 104 are configured to communicateusing one of a variety of frame formats to allow a Fibre Channel frameto be transported over an Ethernet network, such as LAN 100. In thisdescription, the hosts 114 are also referred to as “FCoE hosts,” and theswitches 104 and 106 are also referred to as “FCoE switches”, as theysupport communications in compliance with an FCoE protocol. Accordingly,the host, storage device, and switch ports in the FCoE fabric may bedesignated as FCoE N_PORTs, FCoE F_PORTs, FCoE E_PORTs, and variationsthereof. For example, a port of an FCoE host connected through the FCoEfabric may be designated an FCoE N_PORT, a port of an FCoE switchconnected through the FCoE fabric to an FCoE host may be designated anFCoE F_PORT, and a port of an FCoE switch connected to a port of anotherFCoE switch in the FCoE fabric may be designated as an FCoE E_PORT.

Generally, a developing standard called Fibre Channel over Ethernet(FCoE) allows Fibre Channel (FC) frames to be transmitted and receivedover an Ethernet network. In one implementation, a standard FC frame isequipped with a specified FCoE header and encapsulated within anEthernet frame for communication through the Ethernet network. When anFCoE frame is transmitted through the Ethernet network and reaches aproperly equipped FCoE switch at the boundary of a SAN, the FCoE switchstrips off the Ethernet and FCoE portions of the frame and forwards thepreviously-embedded FC frame through the SAN. Likewise, when a standardFC frame is transmitted through the SAN and reaches a properly equippedFCoE switch at the boundary of the SAN and an Ethernet network, the FCoEswitch adds an FCoE header and an Ethernet header (with appropriatesynchronization fields) to the FC frame and forwards the newly-enhancedFCoE frame to the Ethernet network.

The Ethernet header of the FCoE frame includes source and destination L2addresses, such as MAC addresses, which the Ethernet network uses tocommunicate the frame to its intended destination. For example, hostsand other devices on the Ethernet network can receive the FCoE frame ifthey are configured to receive frames having the MAC address in thedestination field of the Ethernet header. Typically, each host or otherdevice maintains a list of MAC addresses it is configured to receive.Such MAC addresses may be uni-cast addresses, multi-cast addresses,virtual addresses, etc.

FIG. 2 illustrates an example high availability configuration 200including a multipath virtual FCoE switch 202 defined between twophysical FCoE switches 204 and 206. It should be understood that morethan two physical FCoE switches may be configured to provide themultipathing described herein, but only two are shown in FIG. 2 forclarity. In FIG. 2, virtual and/or logical switches, ports and links aredesignated using dashed or dotted lines, whereas physical switches,ports, and links are designated using solid lines.

The physical FCoE switches 204 and 206 provide an interface between anEthernet network (i.e., CEE network 208) and a Fibre Channel fabric 210.In the illustrated example, the physical FCoE switch 204 is designatedas domain 2, and the physical FCoE switch 206 is defined as domain 3. Inaddition, the Fibre Channel fabric 210 is also illustrated as includinga physical FC switch 216 (designated as domain 4) and a physical FCswitch 218 (designated as domain 5). Other fabric configurations arealso contemplated, and it should be understood that the Fibre Channelfabric 210 may also include other physical FC and FCoE switches (notshown). In the illustrated configuration, an FCoE host 212 cancommunicate through the Ethernet network 208 and the FC fabric 210 toand from an FC storage target 214.

However, in one fabric configuration (not shown), the N_PORT of the FCoEhost 212 would communicate through the Ethernet network 208 to an F_PORTof one of the physical FCoE switches 204 or 206. In light of this singlephysical path configuration PORT, if the configured F_PORT becomesdisabled, communications between the FCoE host 212 and the FC storagetarget 214 can be interrupted.

In FIG. 2, however, an alternative implementation is shown. The N_PORTof the FCoE host 212 is physically coupled through the Ethernet network208 to multiple FCoE switch F_PORTs, in this case, F_PORT 220 of theFCoE switch 204 and F_PORT 222 of the FCoE switch 206. The multipathvirtual FCoE switch 202 is created between the FCoE switch 204 and theFCoE switch 206, by a switch configuration circuit of one or both of theswitches, and designated with a domain identifier (ID) that is uniqueamong the domain IDs of the physical switches in the Fibre Channelfabric 210. In one implementation, the multipath virtual FCoE switchcreation is accomplished by a switch configuration circuit of eachphysical FCoE switch defining a virtual FCoE switch having the same,shared domain ID. For example, in the illustrated example, both physicalFCoE switches 204 and 206 define a virtual FCoE switch having a domainID of “1”.

A virtual FCoE switch may be defined as a logical device, implemented ina switch configuration circuit of a physical FCoE switch using softwareand/or firmware. The switch configuration circuit of the physical FCoEswitch assigns a Domain ID to the virtual FCoE switch and adds thevirtual FCoE switch to the FCoE fabric like other physical switches,such that data can flow “through” the virtual FCoE switch between twoports defined on the virtual FCoE switch. Accordingly, the virtual FCoEswitch is incorporated into the routing configuration within the FCoEfabric. Furthermore, one or more virtual FCoE ports may be defined onboth physical and virtual FCoE switches. Each virtual FCoE port is givena unique port address and is incorporated into the routing configurationof the FCoE fabric.

Each physical FCoE switch 204 and 206 defines a virtual FCoE E_PORT foreach of its physical Ethernet-connected F_PORTs, and the multipathvirtual FCoE switch 202 defines a virtual FCoE E_PORT and a logicalInter Switch Link (ISL) for each Ethernet-connected F_PORT of eachphysical FCoE switch 204 and 206 (see logical ISLs 224 and 226). Thelogical ISLs create logical Fabric Shortest Path First (FSPF)adjacencies between the virtual FCoE switch 202 and multipath virtualFCoE E_PORTs of the physical FCoE switches 204 and 206, therebyadvertising the reachability of the multipath virtual FCoE switch 202through the two physical FCoE switches 204 and 206 in the Fibre Channelfabric 210.

For example, two FCoE switches may be considered “logically adjacent”after their topology databases are synchronized. After an FCoE switch(e.g., one of the physical FCoE switches) detects that one of its portsis connected to another switch (e.g. the multipath virtual FCoE switch),it starts exchanging messages with the other FCoE switch, so that bothFCoE switches learn the Domain ID and connected Port ID of the otherFCoE switch. The newly connected ISL is added to the respective topologydatabases of the two FCoE switches, and the FCoE switches exchangetopology database information (whether entirely or differentially) toeffect the full database synchronization. Furthermore, the FCoE switchesissue messages regarding the existence of the newly created logical ISLto other switches in the fabric, thereby allowing the rest of the fabricto learn of the adjacency.

Further, the multipath virtual FCoE switch 202 also defines a virtualFCoE F_PORT for each physical Ethernet-connected F_PORTs of the physicalFCoE switches 204 and 206 that it services. As such, the multipathvirtual FCoE switch 202 has defined two virtual FCoE F_PORTs 228 and 230for communication with the CEE network 208 in the illustrated example.

In one implementation, as specified by an FCoE protocol, the FCoE hostsencapsulate FC frames in FCoE frames for communication to a physicalFCoE switch in the primary FCoE path. The physical FCoE switch removesthe Ethernet and FCoE layers from the received FCoE frame and forwardsthe resulting FC frame to its intended destination. In the reversedirection, the physical FCoE switch receives FC frames for communicationto an FCoE host and encapsulates such frames in FCoE and Ethernet layersfor communication through the CEE network. Implementation variations mayexist, pending approval of different version of the FCoE protocolstandard.

In summary, the illustrated example of a high availability configurationincludes multiple physical communications links between a CEE networkand physical FCoE switches to provide multiple path options into the FCfabric. These multipathing physical FCoE switches define a shared,multipath virtual FCoE switch having its own domain ID. Toward the FCfabric, the multipath virtual FCoE switch defines a virtual FCoE E_PORTand a logical ISL for each physical F_PORT of each physical FCoE switchinterfacing with the CEE network. Each logical ISL “connects” to avirtual FCoE E_PORT defined on each physical FCoE switch. Toward the CEEnetwork, the multipath virtual FCoE switch defines a virtual FCoE F_PORTfor each physical F_PORT of each physical FCoE switch interfacing withthe CEE network. A communications through one of the physical FCoEF_PORTs and switches is defined as the primary communications pathswhile other physical FCoE F_PORTs and switches are held in reserve(e.g., as parts of standby paths) in case the primary FCoE path isdisabled.

FIG. 3 illustrates an example high availability configuration 300including a multipath virtual FCoE switch 302 defined between twophysical FCoE switches 304 and 306 and showing ownership of a MACaddress of a virtual FCoE F_PORT 308. In FIG. 3, virtual and/or logicalswitches, ports and links are designated using dashed or dotted lines,whereas physical switches, ports, and links are designated using solidlines. In the illustrated example, the physical FCoE switch 304 isdesignated as domain 2, and the physical FCoE switch 306 is defined asdomain 3. Furthermore, the multipath virtual FCoE switch 302 is assigneda domain ID equaling 1.

Each of the physical FCoE switches 304 and 306 represents a switch in aFibre Channel fabric 301 and possesses a physical FCoE F_PORT (see 326and 328) connected to a CEE network 316. Each physical FCoE switch hasalso defined a virtual FCoE E_PORT (see 318 and 320).

The multipath virtual FCoE switch 302 has defined with two virtual FCoEE_PORTs 308 and 310 and two virtual FCoE F_PORTs 312 and 314, eachvirtual E_PORT/F_PORT pair corresponding with a physical FCoE F_PORT ofa physical FCoE switch that is connected to a CEE network 316. A logicalISL (see 330 and 332) is defined between each virtual FCoE E_PORT of themultipath virtual FCoE switch 302 and its corresponding virtual FCoEE_PORT of one of the physical FCoE switches.

Each virtual FCoE F_PORT on the multipath virtual FCoE switch 302 isassigned a shared MAC address. At any point, the physical FCoE F_PORT ofthe physical FCoE switch in the primary FCoE path “owns” (“is associatedwith”) the shared MAC address of the corresponding virtual FCoE F_PORTof the multipath virtual FCoE switch 302. In the illustrated example,the primary (active) path is designated through the physical FCoE F_PORT326 of the physical FCoE switch 304, as designated by the bolder signallines (i.e., solid bold lines for the primary physical path and dashedor dotted bold lines for the primary logical path). Therefore, physicalFCoE F_PORT 326 owns the shared MAC address of the virtual FCoE F_PORT308 of the multipath virtual FCoE switch 302. As such, the CEE network316 forwards communications to the physical FCoE F_PORT that owns theshared MAC address (e.g., the shared MAC address is a destinationaddress for the frames being sent from the CEE network 316). Likewise,communications from the physical FCoE F_PORTs use the shared MAC addressas the source address of frames injected into the CEE network 316.

The physical FCoE F_PORT 328 of the physical FCoE switch 306 waits in astandby condition and does not own the shared MAC address (which is alsotermed a “virtual MAC address”). However, if the primary FCoE paththrough the physical FCoE F_PORT 326 of the physical FCoE switch 304fails, the physical FCoE F_PORT 328 of the physical FCoE switch 306 willtake ownership of the shared MAC address to enable frames from the CEEnetwork 316 to be forwarded along the new primary FCoE path through thephysical FCoE F_PORT 328 of the physical FCoE switch 306.

FIG. 4 illustrates an example high availability configuration 400 withcommunications through a primary physical FCoE path 401. In FIG. 4,virtual and/or logical switches, ports and links are designated usingdashed or dotted lines, whereas physical switches, ports, and links aredesignated using solid lines.

The physical FCoE switches 404 and 406 provide an interface between anEthernet network (i.e., CEE network 408) and a Fibre Channel fabric 410.In the illustrated example, the physical FCoE switch 404 is designatedas domain 2, and the physical FCoE switch 406 is defined as domain 3. Inaddition, the Fibre Channel fabric 410 is also illustrated as includinga physical FC switch 416 (designated as domain 4) and a physical FCswitch 418 (designated as domain 5). Other fabric configurations arealso contemplated, and it should be understood that the Fibre Channelfabric 410 may also include other FC and FCoE switches (not shown). Inthe illustrated configuration, an FCoE host 412 can communicate throughthe Ethernet network 408 and the FC fabric 410 to and from an FC storagetarget 414.

The N_PORT of the FCoE host 412 is physically coupled through theEthernet network 408 to multiple FCoE switch F_PORTs, in this case,F_PORT 420 of the FCoE switch 404 and F_PORT 422 of the FCoE switch 406.A multipath virtual FCoE switch 402 is created between the FCoE switch404 and the FCoE switch 406 and designated with a domain ID that isunique among the domain IDs of the physical switches in the FibreChannel fabric 410.

In addition, each physical FCoE switch 404 and 406 defines a virtualFCoE E_PORT for each of its Ethernet-connected F_PORTs, and themultipath virtual FCoE switch 402 defines a virtual FCoE E_PORT and alogical Inter Switch Link (ISL) for each Ethernet-connected F_PORT ofeach physical FCoE switch 404 and 406 (see logical ISLs 424 and 426).Further, the multipath virtual FCoE switch 402 also defines a virtualFCoE F_PORT for each physical Ethernet-connected F_PORTs of the physicalFCoE switches 404 and 406 that it services. As such, the multipathvirtual FCoE switch 402 has defined two virtual FCoE F_PORTs forcommunication with the CEE network 408 in the illustrated example.

When the FCOE host 412 initially sends an FLOGI request into the FibreChannel fabric 410, only one of the physical FCoE switches will respond,i.e., the physical FCoE switch 404 in this case. By allocating a virtualFC ID from the multipath virtual FCoE switch's domain (i.e., 1),responding using the shared MAC address as the source MAC address of theFLOGI ACC, and tying ownership of the virtual MAC address to thephysical FCoE F_PORT 420 using the XF Port assignment process, thephysical FCoE switch 404 configures itself as the primary FCoE path (asindicated by the bold lines). All subsequent FCoE traffic from theN_PORTs of the FCoE host 412 and other FCoE hosts in the CEE network 408(not shown) is directed to the virtual MAC with the virtual FC ID as thesource address. Such N_PORTs discover the targets, perform PLOGIexchanges, and initiate 10 using normal FCoE protocols and processes.The destination FC IDs are not virtualized.

The primary FCoE path operates in the reverse direction as well. Trafficsourced from the FC fabric 410 for delivery into the CEE network 408 isdestined for the domain ID of the multipath virtual FCoE switch 402(i.e., domain ID=1). As domain ID 1 is advertised as being adjacent toboth domain ID 2 and domain ID 3, such traffic is routed to one of thosetwo domains. In one implementation, to ensure that such traffic is onlyrouted to one of those two domains at any one time, the domain in theprimary FCoE path is assigned a lower path cost than any domains instandby paths.

FIG. 5 illustrates example operations 500 for setting up a highavailability configuration with communications through a primaryphysical FCoE path. A creation operation 502 defines a multipath virtualFCoE switch using an Ethernet-connected physical FCoE switch. Thecreation operation 502 also assigns a shared domain ID to the virtualFCoE switch. One or more other Ethernet-connected physical FCoE switchesalso define a virtual FCoE switch, assigning the same shared domain ID.As a result of the multiple virtual FCoE switch definitions, a pluralityof Ethernet-connected physical FCoE switches create a shared, multipathvirtual FCoE switch among them to participate in the multipathing of thehigh availability configuration.

A declaration operation 504 declares a logical adjacency between thephysical FCoE switch and the multipath virtual FCoE switch. Otherphysical FCoE switches sharing the multipath virtual FCoE switch alsodeclare logical adjacency with the shared, multipath virtual FCoEswitch. An assignment operation 506 assigns a multipath virtual MACaddress to a virtual F_PORT of the multipath virtual FCoE switch. Otherphysical FCoE switches sharing the multipath virtual FCoE switch alsoassign the virtual MAC address to a virtual F_PORT of the multipathvirtual FCoE switch so that the virtual FCoE ports of the multipathvirtual FCoE switch share the same virtual MAC address.

A login operation 508 receives a multicast FLOGI request from an FCoEN_PORT on a connected Ethernet network (e.g., from an FCoE host). In oneimplementation, the FCoE N_PORT performs a standard fabric loginprocess—the physical FCoE switches coupled to the CEE network andreceiving the login create the multipathing configuration in response tothe login. A login response operation 510 responds to the FLOGI requestwith an exclusive FLOGI ACC (i.e., only one physical FCoE switchresponds to the FLOGI request). Via the FLOGI ACC response, theresponding physical FCoE switch allocates a virtual FC ID from themultipath virtual FCoE switch's domain and indicates the virtual MACaddress of the virtual FCoE F_PORT. In a tying operation 512, theresponding physical FCoE switch also takes ownership of the virtual MACaddress (e.g., via an XF Port assignment process). As such, the Ethernetnetwork learns of the presence of the virtual FCoE F_PORT on theresponding physical FCoE switch. In this manner, the primary FCoE pathis configured through the responding physical FCoE switch.

A receiving operation 514 and a transmitting operation 516 can operateand repeat in any order, as indicated by the bidirectional arrow 518.The receiving operation 514 receives FCoE frame traffic from the FCoEN_PORT of an FCoE source device through the Ethernet network. Thetraffic is directed to the virtual MAC address, which is recorded in afield of the encapsulating Ethernet and FCoE layers and currently ownedby the responding FCoE switch, and includes the virtual FC ID as thesource address of the encapsulated FC frame.

The responding FCoE switch extracts the FC frame from the FCoEencapsulation and performs normal FC forwarding. For example, a received(de-encapsulated) FC frame is examined to learn the Domain ID and AreaID of the FC ID in the source FC address field. Domain/Area routing isperformed to the physical FC ID in the FC fabric.

The transmitting operation 516 operates in the opposite direction as thereceiving operation 514. FC frame traffic in this operation is destinedto the multipath virtual FCoE switch's domain ID, which is advertised asbeing reachable via one or more of the physical FCoE switches that sharethe multipath virtual FCoE switch. In one implementation, the path costof the physical FCoE switch in the primary FCoE path is set as less thanthe path cost of other physical FCoE switches sharing the multipathvirtual FCoE switch in order to ensure that only the physical FCoEswitch in the primary FCoE path receives the frame traffic destined forthe Ethernet network. The physical FCoE switch in the primary FCoE pathencapsulates the FC frames in Ethernet and FCoE layers and transmits theresulting FCoE frame to the Ethernet network through its physical FCoEF_PORT for delivery to the FCoE N_PORT for which it is destined.

FIG. 6 illustrates an example high availability configuration includinga virtual FCoE switch defined by two physical FCoE switches, after apath switchover. In FIG. 6, virtual and/or logical switches, ports andlinks are designated using dashed or dotted lines, whereas physicalswitches, ports, and links are designated using solid lines.

The physical FCoE switches 604 and 606 provide an interface between anEthernet network (i.e., CEE network 608) and a Fibre Channel fabric 610.In the illustrated example, the physical FCoE switch 604 is designatedas domain 2, and the physical FCoE switch 606 is defined as domain 3. Inaddition, the Fibre Channel fabric 610 is also illustrated as includinga physical FC switch 616 (designated as domain 4) and a physical FCswitch 618 (designated as domain 5). Other fabric configurations arealso contemplated, and it should be understood that the Fibre Channelfabric 610 may also include other FC and FCoE switches (not shown). Inthe illustrated configuration, an FCoE host 612 can communicate throughthe Ethernet network 608 and the FC fabric 610 to and from an FC storagetarget 614.

The N_PORT of the FCoE host 612 is physically coupled through theEthernet network 608 to multiple FCoE switch F_PORTs, in this case,F_PORT 620 of the FCoE switch 604 and F_PORT 622 of the FCoE switch 606.A multipath virtual FCoE switch 602 is created between the FCoE switch604 and the FCoE switch 606 and designated with a domain ID that isunique among the domain IDs of the physical switches in the FibreChannel fabric 610.

In addition, each physical FCoE switch 604 and 606 defines a virtualFCoE E_PORT for each of its Ethernet-connected F_PORTs, and themultipath virtual FCoE switch 602 defines a virtual FCoE E_PORT and alogical Inter Switch Link for each Ethernet-connected F_PORT of eachphysical FCoE switch 604 and 606 (see logical ISLs 624 and 626).Further, the multipath virtual FCoE switch 602 also defines a virtualFCoE F_PORT for each physical Ethernet-connected F_PORTs of the physicalFCoE switches 604 and 606 that it services. As such, the multipathvirtual FCoE switch 602 has defined two virtual FCoE F_PORTs forcommunication with the CEE network 608 in the illustrated example.

In FIG. 6, some aspect of communications through primary FCoE path fails(e.g., the physical FCoE switch 604, the Ethernet-connected F_PORT 620,or the physical link 632 connected to the F_PORT 620). Detection of sucha failure invokes a switchover of the primary FCoE path to one of thestandby paths. If the physical FCoE switch 604 fails, the failure can bedetected by other FC/FCoE switches in the FC fabric 610 upon receipt andprocessing of a domain OFFLINE RSCN, which will result in the updatingof domain routing tables to route along a newly-designated primary FCoEpath (designated by the bold line 601).

In other circumstances, the entire physical FCoE switch 604 may notfail. Instead, only the physical FCoE F_PORT 620 of the physical FCoEswitch 604 may fail or the link 632 may fail. In such circumstances,path re-direction at the port and/or address level may be effected toforce FSPF path re-routing.

The embodiments of the invention described herein are implemented aslogical steps in one or more computer systems. The logical operations ofthe present invention are implemented (1) as a sequence ofprocessor-implemented steps executing in one or more computer systemsand (2) as interconnected machine or circuit modules within one or morecomputer systems. The implementation is a matter of choice, dependent onthe performance requirements of the computer system implementing theinvention. Accordingly, the logical operations making up the embodimentsof the invention described herein are referred to variously asoperations, steps, objects, or modules. Furthermore, it should beunderstood that logical operations may be performed in any order, unlessexplicitly claimed otherwise or a specific order is inherentlynecessitated by the claim language.

The above specification, examples, and data provide a completedescription of the structure and use of exemplary embodiments of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended. Furthermore, structuralfeatures of the different embodiments may be combined in yet anotherembodiment without departing from the recited claims.

What is claimed is:
 1. A method of configuring one or more availableFibre Channel over Ethernet (FCoE) paths in an FCoE fabric, the methodcomprising: defining a virtual FCoE switch connected to both a firstphysical FCoE switch and a second physical FCoE switch, wherein avirtual MAC address of a virtual FCoE F_PORT defined on the virtual FCoEswitch is associated with a physical FCoE F_PORT of the first physicalFCoE switch and not with a physical FCoE F_PORT of the second physicalFCoE switch; and declaring logical adjacency between the first physicalFCoE switch and the virtual FCoE switch.
 2. The method of claim 1wherein the operation of defining a virtual FCoE switch comprises:defining a virtual FCoE switch by the first physical FCoE switch, thevirtual FCoE switch sharing a domain identifier with a virtual FCoEswitch defined by the second physical FCoE switch in the FCoE fabric,the virtual FCoE switches combining to define the multipath virtual FCoEswitch.
 3. The method of claim 1 further comprising: defining thevirtual FCoE F_PORT on the virtual FCoE switch; assigning the virtualMAC address to the virtual FCoE F_PORT of the virtual FCoE switch; andassociating the virtual MAC address to the physical FCoE F_PORT of thefirst physical FCoE switch, wherein the virtual MAC address is notassociated with the physical FCoE F_PORT of the second physical FCoEswitch.
 4. The method of claim 1 further comprising: defining a virtualFCoE E_PORT on the virtual FCoE switch for each of the first and secondphysical FCoE switches; defining a virtual FCoE E_PORT on the firstphysical FCoE switch; and defining a logical Inter Switch Link (ISL)between one of the virtual FCoE E_PORTs on the virtual FCoE switch andthe virtual FCoE E_PORT on the first physical FCoE switch.
 5. The methodof claim 1 further comprising: assigning the virtual MAC address to avirtual FCoE F_PORT defined on the virtual FCoE switch; tying ownershipof the virtual MAC address of the virtual FCoE F_PORT to the physicalFCoE F_PORT of the first physical FCoE switch; and responding to aFabric Login (FLOGI) using the virtual MAC address of the virtual FCoEF_PORT defined on the virtual FCoE switch.
 6. The method of claim 1further comprising: adjusting a relative path cost between the firstphysical FCoE switch and the second physical FCoE switch to route FCoEtraffic through the first physical FCoE switch and to bypass the secondphysical FCoE switch.
 7. A physical FCoE switch comprising: a physicalFCoE F_PORT configured to couple through an Ethernet portion of the FCoEfabric to a physical FCoE N_PORT of an FCoE node through an FCoE fabric;a switch configuration circuit coupled to the physical FCoE F PORT, theswitch configuration circuit defining a virtual FCoE switch between thephysical FCoE switch and the FCoE N_PORT of the FCoE node, wherein avirtual MAC address of a virtual FCoE F_PORT defined on the virtual FCoEswitch is associated with the physical FCoE F_PORT of the physical FCoEswitch and a logical adjacency is declared between the physical FCoEswitch and the virtual FCoE switch.
 8. The physical FCoE switch of claim7 wherein the virtual MAC address of a virtual FCoE F_PORT is shared bythe first physical FCoE switch and a second physical FCoE switch.
 9. Thephysical FCoE switch of claim 7 wherein the virtual FCoE switch isdefined using a virtual FCoE switch defined by the physical FCoE switch,the virtual FCoE switch sharing a domain identifier with a virtual FCoEswitch defined by another physical FCoE switch in the FCoE fabric, thevirtual FCoE switches combining to define a multipath virtual FCoEswitch.
 10. The physical FCoE switch of claim 7 wherein the virtual FCoEswitch is logically connected to the physical FCoE switch and anotherphysical FCoE switch, and the virtual MAC address is not associated to aphysical FCoE F_PORT of the other physical FCoE switch.
 11. The physicalFCoE switch of claim 7 further comprising: a virtual FCoE E_PORT definedon the virtual FCoE switch for each of the physical FCoE switch andanother physical FCoE switch, wherein the virtual FCoE switch islogically connected to both the physical FCoE switch and the otherphysical FCoE switch; a virtual FCoE E_PORT defined on the physical FCoEswitch; and a logical Inter Switch Link (ISL) defined between one of thevirtual FCoE E PORTs on the virtual FCoE switch and the virtual FCoEE_PORT on the physical FCoE switch.
 12. The physical FCoE switch ofclaim 7 wherein ownership of the virtual MAC address of the virtual FCoEF_PORT is tied to the physical FCoE F_PORT of the physical FCoE switch.13. The physical FCoE switch of claim 7 wherein the physical FCoE switchresponds to a Fabric Login (FLOGI) using the virtual MAC address of thevirtual FCoE F_PORT defined on the virtual FCoE switch.
 14. The physicalFCoE switch of claim 7 wherein a multipath virtual FCoE switch isdefined by a virtual FCoE switch of the physical FCoE switch and avirtual FCoE switch of another physical FCoE switch, and a relative pathcost between the physical FCoE switch and the other physical FCoE switchis adjusted to route FCoE traffic through physical FCoE switch and tobypass the other physical FCoE switch.
 15. A Fibre Channel over Ethernet(FCoE) fabric, the FCoE fabric comprising: a first physical FCoE switchcoupled through an Ethernet portion of the FCoE fabric to a physicalFCoE N_PORT of an FCoE node; a second physical FCoE switch coupledthrough the Ethernet portion of the FCoE fabric to the physical FCoEN_PORT of the FCoE node; and a virtual FCoE switch defined by the firstand second physical FCoE switches, wherein a logical adjacency isdeclared between the first physical FCoE switch and the virtual FCoEswitch and a virtual MAC address of a virtual FCoE F_PORT defined on thevirtual FCoE switch is associated with a physical FCoE F_PORT of thefirst physical FCoE switch.
 16. The FCoE fabric of claim 15 wherein, ifthe physical FCoE F_PORT of the first physical FCoE switch fails, thevirtual MAC address of a virtual FCoE F_PORT is associated with aphysical FCoE F_PORT of the second physical FCoE switch.
 17. The FCoEfabric of claim 15 further comprising: virtual FCoE E_PORTs defined onthe virtual FCoE switch for each of the first and second physical FCoEswitches; a virtual FCoE E_PORT defined on each of the first and secondphysical FCoE switches; a first logical Inter Switch Link (ISL) definedbetween one of the virtual FCoE E_PORTs on the virtual FCoE switch andthe virtual FCoE E_PORT of the first physical FCoE switch; and a secondlogical ISL defined between a different one of the virtual FCoE E_PORTson the virtual FCoE switch and the virtual FCoE E_PORT of the secondphysical FCoE switch.
 18. The FCoE fabric of claim 15 wherein ownershipof the virtual MAC address of the virtual FCoE F_PORT is tied to thephysical FCoE F_PORT of the first physical FCoE switch.
 19. The FCoEfabric of claim 15 wherein the first physical FCoE switch responds to aFabric Login (FLOGI) using the virtual MAC address of the virtual FCoEF_PORT defined on the virtual FCoE switch; and if a primary FCoE paththrough the physical FCoE F_PORT of the first physical FCoE switchfails, the second physical FCoE switch responds to the Fabric Login(FLOGI) using the virtual MAC address of the virtual FCoE F_PORT definedon the virtual FCoE switch.
 20. The FCoE fabric of claim 15 wherein amultipath virtual FCoE switch is defined by a virtual FCoE switch of thefirst physical FCoE switch and a virtual FCoE switch of the secondphysical FCoE switch, and a relative path cost between the firstphysical FCoE switch and the second physical FCoE switch is adjusted toroute FCoE traffic through the first physical FCoE switch and to bypassthe second physical FCoE switch.